Image generation apparatus, vehicle, control method of image generation apparatus and storage medium that set an adjustment target value of emission light intensity

ABSTRACT

An image generation apparatus for generating an image includes a light source device; an optical deflection device to deflect laser beam from the light source device to a scanned face arid a light detector; a light quantity adjustment device including a member disposable on a light path of the laser beam between the light source device and the optical deflection device; an emission light intensity adjustment unit to adjust emission light intensity of the light source device; and a controller to set a first adjustment target value of emission light intensity and an adjustment target value of light quantity when laser beam is deflected to the scanned face based on target luminance of the image, and a second adjustment target value of emission light intensity when laser beam is deflected to the light detector based on an adjustment target value of light quantity and detection sensitivity of the light detector.

BACKGROUND

Technical Field

The present invention relates to an image generation apparatus, avehicle, and a control method of an image generation apparatus, and morespecifically, an image generation apparatus that generates an image on ascanned face using laser beam scanning, a vehicle including the imagegeneration apparatus, and a control method of the image generationapparatus.

Background Art

Typically, a headup display apparatus includes, for example, asemiconductor laser, a light quantity adjustment device (e.g., liquidcrystal panel) disposed on a light path of laser beam emitted from thesemiconductor laser to adjust light quantity of the laser beam based ontarget luminance of display image, and an optical deflection device(e.g., MEMS scanner) to deflect the laser beam having adjusted withlight quantity by the light quantity adjustment device toward a scannedface (e.g., surface of a translucent screen) and a light detector (e.g.,color sensor) as disclosed in JP-2013-15738-A. However, as toconventional headup display apparatuses, laser beam may not be detectedeffectively by the light detector depending on levels of targetluminance.

SUMMARY

In one aspect of the present invention, an image generation apparatusfor generating an image by scanning a scanned face using laser beam isdevised. The image generation apparatus includes a light source devicehaving at least one semiconductor laser; an optical deflection device todeflect laser beam from the light source device to the scanned face anda light detector; a light quantity adjustment device including a memberdisposable on a light path of the laser beam between the semiconductorlaser and the optical deflection device to adjust light quantity of thelaser beam; an emission light intensity adjustment unit to adjustemission light intensity of the semiconductor laser; and a controller toset a first adjustment target value of the emission light intensity,which is an adjustment target value of the emission light intensity, andan adjustment target value of the light quantity when laser beam isdeflected to the scanned face by the optical deflection device based ontarget luminance of the image, and a second adjustment target value ofthe emission light intensity, which is an adjustment target value of theemission light intensity, when laser beam is deflected to the lightdetector by the optical deflection device based on an adjustment targetvalue of the light quantity and detection sensitivity of the lightdetector.

In another aspect of the present invention, a method of controlling ofan image generation apparatus generating an image by scanning a scannedface using laser beam is devised. The image generation apparatusincludes a light source device having at least one semiconductor laser;an optical deflection device to deflect laser beam from the light sourcedevice to the scanned face and a light detector; a light quantityadjustment device including a member disposable on a light path of thelaser beam between the semiconductor laser and the optical deflectiondevice to adjust light quantity of the laser beam; an emission lightintensity adjustment unit to adjust emission light intensity of thesemiconductor laser, the method includes: setting a first adjustmenttarget value of the emission light intensity which is an adjustmenttarget value of the emission light intensity and adjustment target valueof the light quantity when laser beam is deflected to the scanned faceby the optical deflection device based on target luminance of the image;and setting a second adjustment target value of the emission lightintensity which is an adjustment target value of the emission lightintensity when laser beam is deflected to the light detector by theoptical deflection device based on an adjustment target value of thelight quantity and detection sensitivity of the light detector.

In another aspect of the present invention, a non-transitorycomputer-readable storage medium storing a program that, when executedby a computer having a processing circuit, causes the computer toexecute a method of controlling of an image generation apparatusgenerating an image by scanning a scanned face using laser beam isdevised. The image generation apparatus includes a light source devicehaving at least one semiconductor laser; an optical deflection device todeflect laser beam from the light source device to the scanned face anda light detector; a light quantity adjustment device including a memberdisposable on a light path of the laser beam between the semiconductorlaser and the optical deflection device to adjust light quantity of thelaser beam; an emission light intensity adjustment unit to adjustemission light intensity of the semiconductor laser, the methodincludes: setting a first adjustment target value of the emission lightintensity which is an adjustment target value of the emission lightintensity and adjustment target value of the light quantity when laserbeam is deflected to the scanned face by the optical deflection devicebased on target luminance of the image; and setting a second adjustmenttarget value of the emission light intensity which is an adjustmenttarget value of the emission light intensity when laser beam isdeflected to the light detector by the optical deflection device basedon an adjustment target value of the light quantity and detectionsensitivity of the light detector.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages and features thereof can be readily obtained and understoodfrom the following detailed description with reference to theaccompanying drawings, wherein:

FIG. 1 is a schematic configuration of a headup display apparatusaccording to an example embodiment;

FIG. 2 is a schematic configuration of an optical deflection device anda lens array of FIG. 1;

FIG. 3 is an example of a scanning pattern of laser beam on the lensarray;

FIG. 4 is a view showing a positional relationship of effective scanningarea (image drawing area) on the lens array and a light detector;

FIG. 5 is one example of a light adjustment member of a light quantityadjustment device;

FIG. 6 is a graph showing a relationship of driver current (I) of alaser diode and laser beam intensity (P);

FIG. 7 is a flowchart showing the steps of a control process of a headupdisplay;

FIG. 8 is a table showing a relationship of target luminance, adjustmenttarget value of transmittance and adjustment target value of drivecurrent;

FIG. 9 is a schematic configuration of a headup display apparatus ofvariant example 1;

FIG. 10 is a flowchart showing the steps of control process of theheadup display of the variant example 1;

FIG. 11 is a schematic configuration of one example of projector;

FIG. 12 is another example of an optical deflection device;

FIG. 13 is another example of a light adjustment member; and

FIG. 14 is a schematic configuration of a headup display apparatus ofvariant example 2.

The accompanying drawings are intended to depict exemplary embodimentsof the present invention and should not be interpreted to limit thescope thereof. The accompanying drawings are not to be considered asdrawn to scale unless explicitly noted, and identical or similarreference numerals designate identical or similar components throughoutthe several views.

DETAILED DESCRIPTION

A description is now given of exemplary embodiments of the presentinvention. It should be noted that although such terms as first, second,etc. may be used herein to describe various elements, components,regions, layers and/or sections, it should be understood that suchelements, components, regions, layers and/or sections are not limitedthereby because such terms are relative, that is, used only todistinguish one element, component, region, layer or section fromanother region, layer or section. Thus, for example, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the present invention.

In addition, it should be noted that the terminology used herein is forthe purpose of describing particular embodiments only and is notintended to be limiting of the present invention. Thus, for example, asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. Moreover, the terms “includes” and/or “including”, when usedin this specification, specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

Furthermore, although in describing views shown in the drawings,specific terminology is employed for the sake of clarity, the presentdisclosure is not limited to the specific terminology so selected and itis to be understood that each specific element includes all technicalequivalents that have a similar function, operate in a similar manner,and achieve a similar result. Referring now to the drawings, anapparatus or system according to an example embodiment is describedhereinafter.

A description is given of an example embodiment with reference to FIG. 1to FIG. 8. FIG. 1 is a schematic configuration of a headup displayapparatus 7, which is an example of an image generation apparatusaccording to an example embodiment. In this description, XYZ threedimensional orthogonal coordinate system is used by setting Z-axisdirection as the vertical direction as illustrated in FIG. 1 and otherdrawings, and the headup display apparatus 7 may be also referred to asthe HUD apparatus 7.

The HUD apparatus 7 can be equipped to, for example, automobiles, airplanes, ships or the like (hereinafter, referred to as “vehicle”), withwhich a driver or operator (hereinafter referred to as “driver”) canview information of driving, operation, or running (hereinafter referredto as “driving”) of the vehicle through a windshield of the vehicle.

As illustrated in FIG. 1, the HUD apparatus 7 includes, for example, alight source device 15, a light quantity adjustment device 30, anoptical deflection device 40, a lens array 60, a semi-translucent member70, a light detector 150 (FIG. 4), a control unit 1000, and an operationpanel.

The light source device 15 includes, for example, three laser diodes LD1to LD3, three collimate lenses CR1 to CR3, and three dichroic mirrorsDM1 to DM3. The laser diode is, for example, an edge emitting laser,which is one type of semiconductor lasers.

The laser diode LD1 is, for example, red laser disposed at a position toemit red light (wavelength of 640 nm) to +Z direction.

The laser diode LD2 is, for example, blue laser disposed at +X sideposition of the laser diode LD1 to emit blue light (wavelength of 450nm) to +Z direction.

The laser diode LD3 is, for example, green laser disposed at +X sideposition of the laser diode LD2 to emit green light (wavelength of 520nm) to +Z direction.

The collimate lens CR1 is, for example, disposed at +Z side of the laserdiode LD1 to set red light emitted from the laser diode LD1 tosubstantially parallel light.

The collimate lens CR2 is, for example, disposed at +Z side of the laserdiode LD2 to set blue light emitted from the laser diode LD2 tosubstantially parallel light.

The collimate lens CR3 is, for example, disposed at +Z side of the laserdiode LD3 to set green light emitted from the laser diode LD3 tosubstantially parallel light.

Each of the three dichroic mirrors DM1 to DM3 is made of, for example, athin film such as dielectric multilayer that reflects light havingspecific wavelength and passes through light having other wavelength.

The dichroic mirror DM1 is, for example, disposed at +Z side of thecollimate lens CR1 while slanted, for example, 45 degrees with respectto X-axis and Z-axis to reflect red light coming from the collimate lensCR1 to +X direction.

The dichroic mirror DM2 is, for example, disposed at +X side of thedichroic mirror DM1 and at +Z side of the collimate lens CR2 whileslanted, for example, 45 degrees with respect to X-axis and Z-axis topass through red light coming from the dichroic mirror DM1 to +Xdirection, and to reflect blue light coming from the collimate lens CR2to +X direction.

Further, red light coming from the dichroic mirror DM1 and blue lightcoming from the collimate lens CR2 enter near the center of the dichroicmirror DM2.

The dichroic mirror DM3 is, for example, disposed at +X side of thedichroic mirror DM2 and at +Z side of the collimate lens CR3 whileslanted, for example, 45 degrees with respect to X-axis and Z-axis topass through red light and blue light coming from the dichroic mirrorDM2 to +X direction, and to reflect green light coming from thecollimate lens CR3 to +X direction.

Further, red light and blue light coming from the dichroic mirror DM2and green light coming from the collimate lens CR3 enter near the centerof the dichroic mirror DM3.

Three lights (i.e., red light, blue light and green light) passing thedichroic mirror DM3 are synthesized as one light, in which the color ofsynthesized light can be generated based on balance of emission lightintensity of the three laser diodes LD1 to LD3.

Therefore, the light source device 150 emits a laser beam (i.e.,synthesized light) synthesizing three laser beams from the three laserdiodes LD1 to LD3 to +X direction.

The light quantity adjustment device 30 includes, for example, a lightadjustment member 32 and an actuator 34. The light adjustment member 32is disposed on a light path of laser beam (i.e., synthesized light)coming from the light source device 15 such as +X side of the dichroicmirror DM3. The actuator 34 drives the light adjustment member 32 inY-axis direction.

The light adjustment member 32 includes, for example, a plurality oflight passing portions 32 a to 32 e (e.g., five light passing portions)arranged in Y-axis direction while having different transmittance oflaser beam with each other as illustrated in FIG. 5. The five lightpassing portions 32 a to 32 e are arranged in Y-axis direction with theorder of transmittance Tn (n is natural number) of laser beam, and thetransmittance Tn of the light passing portions 32 a to 32 e arerespectively set with T1 to T5 having the order of “T1<T2<T3<T4<T5.”

The controller 300, to be described later, controls the actuator 34 sothat any one of the five light passing portions 32 a to 32 e ispositioned on a light path of laser beam coming from the light sourcedevice 15. In this configuration, light quantity of the laser beamcoming from the light source device 15 after passing the lightadjustment member 32 is reduced compared to light quantity of the laserbeam before passing the light adjustment member 32. The controller 300controls the actuator 34 based on detection information from a sensorthat detects position information of the light adjustment member 32 inY-axis direction.

The actuator 34 can be, for example, a screw-feed device, a rack andpinion device, a linear motor device, a cylinder device that can drivethe light adjustment member 32 at least along one axis direction (e.g.,Y-axis direction).

As illustrated in FIG. 2, the optical deflection device 40 includes, forexample, a mirror 40 a (e.g. MEMS mirror) disposed on a light path oflaser beam passing through the light adjustment member 32. The laserbeam entering the mirror 40 a can be deflected to the lens array 60 andthe light detector 150 (see FIG. 4).

For example, the mirror 40 a can independently oscillate about two axesperpendicular to each other, wherein a first axis is parallel to Y-axis,and a second axis is perpendicular to the first axis. The opticaldeflection device 40 includes the mirror 40 a, a mirror drive unit thatdrives the mirror 40 a about each axis, and an angle detector thatdetects deflection angle of the mirror 40 a about each axis. The angledetector outputs a signal corresponding to a deflection angle of themirror 40 a about each axis to a mirror control unit 400 (see FIG. 1) tobe described later. The optical deflection device 40 can be manufacturedusing semiconductor manufacturing technology process such as microelectro mechanical systems (MEMS) process.

The lens array 60 is, for example, disposed on a light path of laserbeam deflected by the optical deflection device 40 such as +Z side ofthe optical deflection device 40. A surface such as a scanned face ofthe lens array 60 is two-dimensionally scanned by the laser beam in themain scanning direction (direction corresponding to the second axis) andthe sub-scanning direction (direction corresponding to the first axis)perpendicular to each other to form an image. For example, the mainscanning direction is Y-axis direction, and the sub-scanning directionis X-axis direction. An image formed on a surface of the lens array 60may be referred to as “projection image.”

As illustrated in FIGS. 2 and 3, the lens array 60 includes a pluralityof micro lenses 60 a (see FIG. 1) arranged in matrix or a latticepattern in X-axis direction and Y-axis direction, wherein each of themicro lenses 60 a is a hemisphere lens convex to +Z side. The diameterof each of the micro lenses 60 a is set greater than a beam diameter oflaser beam. Further, each of the micro lenses 60 a is corresponded toone pixel of a projection image. Therefore, the lens array 60 canfunction as a diffusing plate that diffuses a laser beam correspondingto each pixel of the projection image.

In a configuration of FIG. 1, the semi-translucent member 70 is alsoreferred to as a combiner, and is disposed on a light path of laser beamcoming from the lens array 60 such as +Z side of the lens array 60. Thesemi-translucent member 70 is, for example, a plate disposed whileslanted to XY-plane.

A part of the laser beam coming from the lens array 60 passes thesemi-translucent member 70, and remaining part of the laser beam isreflected by the semi-translucent member 70. With this configuration, anobserver or viewer can view a virtual image, which is an expanded viewof an image formed on a surface (i.e., scanned face) of the lens array60 via the semi-translucent member 70.

If the diffusing plate such as the lens array 60 is not used, laser beamis scattered on the semi-translucent member 70, and the scattered lightinterferes on retina of the observer or viewer, with which speckle noiseoccurs. By contrast, by using the lens array 60, a field of view of theobserver or viewer can be secured by laser beam diffused by each of themicro lenses 60 a, with which speckle noise can be reduced greatly.

To be described later, the light detector 150 is disposed on a lightpath of laser beam deflected by the optical deflection device 40. Thelight detector 150 is, for example, a photo diode, a photo transistor orthe like. When the light detector 150 detects laser beam deflected bythe optical deflection device 40, the light detector 150 outputs adetection result (e.g., light quantity and color information) to thecontroller 300 to be described later.

As illustrated in FIG. 1, the control unit 1000 includes, for example,an image processing unit 100, the controller 300, a mirror control unit400, and a laser diode (LD) control unit 500.

The image processing unit 100 conducts various processing such as signalconversion, color correction, distortion correction, resolutionconversion, image size conversion corresponding to pixel numbers andfrequency for image information transmitted from an image data outputapparatus such as personal computer (PC), memory, hard disk, diskplayer, television conference terminal, tablet terminal, or smart phone,and transmits the processed image information to the controller 300.Further, the above image information includes, for example, informationof driving of vehicle.

The controller 300 transmits the image information received from theimage processing unit 100 to the LD control unit 500. Further, thecontroller 300 generates a synchronizing signal based on a signalcorresponding to a deflection angle received from the mirror controlunit 400, and outputs the synchronizing signal to the LD control unit500.

Further, based on target luminance input from a target luminance inputunit 600 and detection sensitivity of the light detector 150, thecontroller 300 controls the light quantity adjustment device 30 and theLD control unit 500, in which the controller 300 adjusts projectionimage luminance at the target luminance, and also adjusts light quantityof laser beam directed to the light detector 150 at a level that can bedetected by the light detector 150. The target luminance input unit 600is to be described later.

In this configuration, based on the target luminance of projectionimage, the controller 300 sets an adjustment target value of lightquantity by the light quantity adjustment device 30 (i.e., transmittanceof the light adjustment member 32), and an adjustment target value ofemission light intensity by the LD control unit 500 (i.e., drive currentvalue of each laser diode) to be described later. The controller 300includes a memory used as a storage unit that can store a table (seeFIG. 8) having information of combination of transmittance Tn of thelight adjustment member 32 and drive current value Ik of each laserdiode, which can be used for adjusting projection image luminance totarget luminance Lm, and for adjusting light quantity of laser beamdeflected to the light detector 150 at a level that can be detected bythe light detector 150.

Further, the controller 300 corrects white balance of an image (i.e.,projection image) formed on the surface of the lens array 60. Forexample, the controller 300 adjusts white balance of a projection imagebased on a correction-use table having pre-stored property of the threelaser diodes LD1 to LD3 corresponding to RGB, and coefficient based onproperty of the light adjustment member 32, and detection result (e.g.,light quantity and color information) at the light detector 150, andtransmits an adjustment result to the LD control unit 500, and correctswhite balance via the LD control unit 500.

The mirror control unit 400 adjusts power to be supplied to the mirrordrive unit based on a signal corresponding to a deflection angle of themirror 40 a about each axis received from the angle detector. Further,the mirror control unit 400 transmits the signal corresponding to thedeflection angle of the mirror 40 a about each axis received from theangle detector to the controller 300.

The LD control unit 500 can adjust emission light intensity (i.e., drivecurrent value) of the three laser diodes LD1 to LD3 independently,generates a modulated signal based on image information from thecontroller 300, and supplies drive current corresponding to themodulated signal at a given timing after receiving a synchronizingsignal from the controller 300 to each of laser diodes. With thisconfiguration, the laser beam modulated based on the image informationcan be emitted from each of laser diodes under a condition synchronizedwith a deflection angle of the mirror 40 a about each axis. The LDcontrol unit 500 can be used as an emission light intensity adjustmentunit.

Further, based on the synchronizing signal from the controller 300, theLD control unit 500 can adjust emission light intensity (i.e., drivecurrent value) of each of laser diodes independently for a first caseand a second case, wherein the first case is when the optical deflectiondevice 40 deflects the laser beam to the surface (i.e., scanned face) ofthe lens array 60, and the second case is when the optical deflectiondevice 40 deflects the laser beam to the light detector 150. Forexample, drive current value Ik (k is natural number) when laser beam isdeflected to an image drawing area can be set any one of “I1” to “I4”set with the order of “I1<I2<I3<I4” (see FIG. 8), and the drive currentvalue Ik when the laser beam is deflected to the light detector 150 isset I4 (see FIG. 8).

In this configuration, the drive current value I4 is set to a givenvalue so that laser beam, emitted from a laser diode supplied with thedrive current value I4 and passing the light passing portion 32 a havingtransmittance T1, can be detected by the light detector 150 (i.e.,intensity of laser beam is set to a minimum value or more detectable bythe light detector 150), which means the drive current value I4 is setbased on transmittance T1, and detection sensitivity of the lightdetector 150.

Further, based on the adjustment result of white balance received fromthe controller 300, the LD control unit 500 conducts fine adjustment ofemission light intensity of each of laser diodes to correct whitebalance. The fine adjustment can be conducted by adjusting drive currentvalue of at least one laser diode so that drive current value of each oflaser diodes becomes a value close to the set drive current value Ik.

The laser diode has intensity property of laser beam with respect todrive current as illustrated in FIG. 6, in which one current value isset as a threshold value (i.e., threshold current Ith) and property isdifferent in an area of the threshold current “Ith” or more, and an areaof the threshold current “Ith” or less. Typically, when a drive currentvalue is the threshold current Ith or more, a relationship of drivecurrent value and intensity property of laser beam can be assumed aslinear, and thereby suitable control can be conducted. However, when adrive current value is the threshold current Ith or less, laser emissionis not conducted. Further, because a level of threshold current Ith andemission property is different for each of lasers, it is difficult tosecure appropriate white balance for a projection image.

Therefore, if target luminance is set less than a given value, it isdifficult to adjust projection image luminance and color correctly byonly adjusting emission light intensity of laser diode.

In view of such issue, in an example embodiment, even if targetluminance is set low (e.g., less than a given value), by combining lightquantity adjustment by the light quantity adjustment device 30 andemission light intensity adjustment by the LD control unit 500,luminance adjustment can be conducted using drive current of Ith ormore, and projection image luminance and image quality (e.g., whitebalance) can be adjusted correctly, in which drive current value I1 isset to the threshold current Ith or more (drive current valueI1≧threshold current Ith) as indicated in FIG. 6. Further, because thethreshold current Ith is different for each of lasers (i.e., variance orfluctuation), the driver current I1 is preferably set slightly greaterthan the threshold current Ith (i.e., design value). If projection imageluminance is to be adjusted at a low luminance area such as severalcd/m² by only adjusting the emission light intensity of the laser diode,drive current is required to be controlled at less than the thresholdcurrent Ith, in which it is difficult to correctly adjust projectionimage luminance and color.

The operation panel includes operation members for setting varioussettings, and the target luminance input unit 600 (FIG. 1) to inputtarget luminance manually by a driver or user. The target luminanceinput unit 600 can set target luminance at a plurality of levels (e.g.,eight levels of L1 to L8) depending on brightness around the HUDapparatus 7 (FIG. 8). In this configuration, for example, the targetluminance is not an exact target value of luminance but a givenluminance range can be used as the target luminance. In view ofvisibility of a virtual image of a projection image, the targetluminance is preferably set higher as brighter around the HUD apparatus7. The target luminance set by the target luminance input unit 600 istransmitted to the controller 300. Further, the target luminance inputunit 600 can be used to input an exact luminance value as the targetluminance.

In a case of a vehicle-mounted HUD apparatus, luminance of severalthousands to several tens of thousands cd/m² is required under brightenvironment such as day light, and luminance is required to be reducedat several cd/m² under dark environment such as night and tunnel forviewing a virtual image of projection image,

As illustrated in FIG. 3, the lens array 60 is reciprocally scanned bylaser beam along the main scanning direction with a high speed andscanned along the sub-scanning direction with a low speed, in which araster scan is conducted by scanning scan lines extending along the mainscanning direction in the sub-scanning direction.

Specifically, by controlling the optical deflection device 40, the laserbeam can be moved reciprocally in the main scanning direction (e.g.,Y-axis direction) with high speed using resonance of the mirror 40 a,and the laser beam can be moved in the sub-scanning direction (e.g., −Xdirection) at a constant speed without resonance.

As illustrated in FIG. 4, the light detector 150 is, for example,disposed with the lens array 60 by positioning the light detector 150 ata position outside an effective scanning area of the lens array 60 inthe main scanning direction. The effective scanning area is an imagedrawing area where an image is actually drawn or formed, which is asurface (i.e., scanned face) of the lens array 60.

The mirror control unit 400 controls a deflection angle of the mirror 40a so that the laser beam deflected by the optical deflection device 40enters a marker area including the light detector 150 by setting thelight detector 150 in the marker area. Further, because the lightdetector 150 is disposed at a position outside the image drawing area asdescribed above, even if the laser beam is deflected to the lightdetector 150, projection image is not affected.

In this configuration, based on detection timing of laser beam at thelight detector 150, an amplitude of projection image in the mainscanning direction (e.g., Y-axis direction) and the sub-scanningdirection (e.g., X-axis direction) can be controlled. Further, based ona detection result (e.g., light quantity and color information) at thelight detector 150, the above described white balance adjustment can beconducted. Further, because a maximum deflection angle about the firstaxis and second axis fluctuates due to some factors such as temperatureproperty of the mirror 40 a and structural fluctuation of the mirrordrive unit, the amplitude control is conducted to cope with suchfluctuations.

To enhance visibility of a virtual image of projection image viewablevia the semi-translucent member 70, projection image luminance isrequired to be adjusted to target luminance corresponding to brightnessaround the HUD apparatus 7.

A description is given of a control method of the HUD apparatus 7 withreference to FIGS. 7 and 8. FIG. 7 is a flowchart of showing the stepsof process algorithm of the controller 300. The controller 300 reads atable illustrated in FIG. 8 from a memory, and controls the lightquantity adjustment device 30 and the LD control unit 500 by referringthe table.

This control flow can be started when, for example, a driver inputs orsets desired target luminance Lm (m is natural number) using the targetluminance input unit 600 in view of brightness level around the HUDapparatus 7. For example, as illustrated in FIG. 8, the target luminanceLm can be set any one of eight target luminance's L1 to L8 set with theorder of “L1<L2<L3<L4<L5<L6<L7<L8.”

At step S1, it is determined whether the input target luminance Lm is athreshold value TH or more. In this configuration, the threshold valueTH is set to a minimum value of luminance that can be detected by thelight detector 150 or a value greater than the minimum value for somevalue, in which the threshold value TH is set based on detectionsensitivity of the light detector 150. For example, the threshold valueTH is set as “L3<threshold value TH≦L4.” In this case, if the inputtarget luminance Lm at step S1 is L4 to L8, determination at step S1 canbe affirmed (YES), and then the process proceeds to step S3. If theinput target luminance Lm at step S1 is L1 to L3, determination at stepS1 cannot be affirmed (NO), then the process proceeds to step S9.

At step S3, transmittance Tn (i.e., adjustment target value of lightquantity) is set to a value of transmittance T1 to T5 corresponding tothe input target luminance Lm (e.g., L4 to L8), and based on a settingresult of transmittance Tn, the light quantity adjustment device 30 iscontrolled. Specifically, as illustrated in FIG. 8, it is controlled tobecome transmittance Tn as T1 to T5 for the target luminance L4 to L8,which means the actuator 34 is controlled to position the light passingportions 32 a to 32 e on a light path of laser beam coming from thelight source device 15. Further, if drive current value Ik is set I4 fortransmittance T1 to T5, projection image luminance can be adjusted tothe target luminance L4 to L8 and laser beam can be detected at thelight detector 150 (see FIG. 8).

At step S5, drive current value Ik (i.e., first and second adjustmenttarget values of emission light intensity) is set to I4, and a settingresult (e.g., I4) is output to the LD control unit 500. Then, the LDcontrol unit 500 supplies the drive current I4 to each of laser diodes.With this configuration, laser beam (i.e., synthesized light) matched tothe drive current I4 can be emitted from the light source device 15,pass through one of the five light passing portions 32 a to 32 e, andthen the laser beam is deflected by the optical deflection device 40 tothe lens array 60 and the light detector 150. With this configuration,projection image luminance can be adjusted to the target luminance L4 toL8, and laser beam can be detected by the light detector 150. Upondetecting the laser beam, the light detector 150 outputs a detectionresult (e.g., light quantity and color information) to the controller300.

At step S7, as described above, based on the correction-use table andthe detection result (e.g., light quantity and color information)received from the light detector 150, white balance is adjusted, and anadjustment result of white balance is output to the LD control unit 500.Then, the LD control unit 500 conducts a fine adjustment of drivecurrent value Ik to be supplied to each of laser diodes based on theadjustment result of white balance to correct white balance of aprojection image.

At step S8, based on detection timing of laser beam at the lightdetector 150, the optical deflection device 40 is controlled to conductamplitude control of projection image in the main scanning direction andthe sub- scanning direction. When step S8 is conducted, the processends.

At step S9, transmittance Tn (i.e., adjustment target value of lightquantity) is set to T1, and based on a setting result of transmittanceTn (e.g., T1), the light quantity adjustment device 30 is controlled.Specifically, as illustrated in FIG. 8, to set transmittance Tn as T1for the target luminance L1 to L3, the actuator 34 is controlled toposition the light passing portion 32 a on a light path of laser beamcoming from the light source device 15. Further, if drive current valueIk is I1 to I3 for transmittance T1, projection image luminance can beadjusted to the target luminance L1 to L3 (see FIG. 8).

At step S11, drive current value Ik (i.e., first adjustment target valueof emission light intensity) when laser beam is deflected to an imagedrawing area (i.e., scanned face) by the optical deflection device 40 isset to I1 to I3 corresponding to the target luminance L1 to L3, and isoutput to the LD control unit 500. Then, the LD control unit 500supplies the drive current I1 to I3 to each of laser diodes. With thisconfiguration, laser beam having intensity matched to the drive currentI I1 to I3 can be emitted from each of laser diodes, and enters the lensarray 60 via the light passing portion 32 a. With this configuration,projection image luminance can be adjusted to the target luminance L1 toL3.

At step S13, drive current value Ik (i.e., second adjustment targetvalue of the emission light intensity) when laser beam is deflected tothe light detector 150 by the optical deflection device 40 is set to I4,and a setting result of drive current value Ik (e.g., I4) is output tothe LD control unit 500. Then, the LD control unit 500 supplies thedrive current I4 to each of laser diodes. With this configuration, laserbeam having intensity matched to the drive current I4 can be emittedfrom each of laser diodes, and pass through the light passing portion 32a, and then the laser beam is deflected to the light detector 150 by theoptical deflection device 40. With this configuration, the lightdetector 150 can detect the laser beam. Upon detecting the laser beam,the light detector 150 outputs a detection result (e.g., light quantityand color information) to the controller 300. When step S13 isconducted, the process proceeds to step S7.

The above described processing can be conducted when target luminance ofprojection image is changed (or input) each time to adjust projectionimage luminance at desired luminance.

The above described HUD apparatus 7 includes the light source device 15having three laser diodes, the optical deflection device 40 thatdeflects laser beam coming from the light source device 15 to thescanned face such as the surface of the lens array 60, the lightdetector 150, the light quantity adjustment device 30 that can positionthe light adjustment member 32 on a light path of laser beam between thelight source device 15 and the optical deflection device 40 to adjustlight quantity (i.e., light transmittance) of the laser beam, the LDcontrol unit 500 that adjusts emission light intensity of each of laserdiodes (i.e., drive current value), and the controller 300. Thecontroller 300 can set the first adjustment target value of emissionlight intensity (i.e., drive current value Ik) and an adjustment targetvalue of the light quantity (i.e., transmittance Tn) when laser beam isdeflected to a scanned face by the optical deflection device 40 based ontarget luminance Lm of a projection image, and the second adjustmenttarget value of the emission light intensity (i.e., drive current valueIk) when laser beam is deflected to the light detector 150 by theoptical deflection device 40 based on the detection sensitivity of thelight detector 150 and an adjustment target value of the light quantity(i.e., transmittance Tn).

In this configuration, when laser beam is deflected to the scanned faceby the optical deflection device 40, emission light intensity of each oflaser diodes can be adjusted to the adjustment target value (e.g., I1 toI4) by the LD control unit 500, and light quantity of laser beam comingfrom the light source device 15 can be adjusted to the adjustment targetvalue (e.g., T1 to T5) by the light quantity adjustment device 30. Withthis configuration, projection image luminance can be adjusted to thetarget luminance of L1 to L8.

Further, when laser beam is deflected to the light detector 150 by theoptical deflection device 40, emission light intensity of each of laserdiodes can be adjusted to the adjustment target value (e.g., I4) by theLD control unit 500, and light quantity of laser beam coming from thelight source device 15 can be adjusted to the adjustment target value(e.g., T1 to T5) by the light quantity adjustment device 30. With thisconfiguration, the light detector 150 can detect laser beam.

With this configuration, as to the HUD apparatus 7, projection imageluminance can be adjusted to target luminance, and the light detectorcan detect laser beam for any levels of target luminance.

As to conventional headup display apparatuses, light quantity of laserbeam is adjusted by a light quantity adjustment device (e.g., liquidcrystal panel) based on target luminance, and the laser beam isdeflected to a scanned face (e.g., surface of translucent screen) and alight detector (e.g., color sensor) by an optical deflection device(e.g., MEMS scanner). Therefore, the light detector cannot detect laserbeam depending on level of target luminance such as when the level oftarget luminance becomes less than the minimum luminance that can bedetected by the light detector, in which image quality adjustment andimage amplitude control cannot be conducted.

Further, if the target luminance Lm is less than the threshold value TH,set based on the detection sensitivity of the light detector 150, thecontroller 300 can set the second adjustment target value of emissionlight intensity greater than the first adjustment target value ofemission light intensity, with which the light detector 150 can detectlaser beam even if the target luminance Lm is low.

Further, because the controller 300 can set the first adjustment targetvalue of emission light intensity (i.e., drive current value Ik) same orgreater than emission light intensity corresponding to the thresholdcurrent Ith of laser emission at each of laser diodes, the laser diodecan be stably emitted, and projection image luminance can be adjustedstably with high precision.

Further, because the controller 300 can adjust white balance of aprojection image based on a detection result at the light detector 150,white balance adjustment can be conducted effectively even if the targetluminance Lm is low.

Further, because the controller 300 can control the optical deflectiondevice 40 based on detection timing of laser beam at the light detector150, image amplitude control can be conducted effectively even if thetarget luminance Lm is low.

Further, the light quantity adjustment device 30 includes the lightadjustment member 32 including the five light passing portions 32 a to32 e having different transmittance of laser beam with each other.Therefore, by positioning any one of the five light passing portions 32a to 32 e on a light path of laser beam coming from the light sourcedevice 15, light quantity of the laser beam can be adjusted to theadjustment target value (Tn).

Further, as to the HUD apparatus 7, a light source employs a laserdiode, with which color area can be enlarged and color reproducibilitycan be enhanced. Further, compared to using a lamp as a light source,power consumption of a laser diode can be reduced greatly, and apparatussize can be smaller.

Further, as to the LD control unit 500, emission light intensity of thethree laser diodes LD1 to LD3 can be adjusted independently, with whichdesired monochrome image and color image can be formed, and colorcorrection such as white balance adjustment can be conducted easily.

Further, as to the HUD apparatus 7, because the lens array 60 (i.e.,light translucent member) having a scanned face is disposed on a lightpath of laser beam deflected by the optical deflection device 40, imagelight formed on a scanned face can be diffused and passed. With thisconfiguration, a driver can view a virtual image, which is an expandedimage formed on the scanned face, via the semi-translucent member 70.Further, occurrence of speckle noise on the semi-translucent member 70can be reduced. With this configuration, visibility of a virtual imagevia the semi-translucent member 70 can be enhanced.

A vehicle (e.g., automobile, train) including the above described HUDapparatus 7, and a windshield can be provided. The windshield, used as alight translucent window, is disposed on a light path of light deflectedby the optical deflection device 40 and passing the lens array 60 of theHUD apparatus 7 (e.g., −X side of the semi-translucent member 70 in FIG.1). As to this vehicle, a virtual image having good visibility can begenerated or formed through the windshield by the HUD apparatus 7 forany levels of brightness of environment around the HUD apparatus, withwhich a driver can view information for driving easily. Further, insteadof providing the semi-translucent member 70, a windshield of a vehiclecan be functioned as the semi-translucent member 70.

Further, instead of the lens array 60, for example, a translucent screen(i.e., light translucent member) can be used. Further, for example, amirror such as a concave mirror and a flat mirror can be disposed on alight path between the light translucent member (e.g., lens array 60,translucent screen) and the semi-translucent member 70.

As above described, as to the HUD apparatus 7, image quality adjustmentand amplitude control of projection image using the light detector 150can be conducted, and projection image luminance can be adjusted whilemaintaining suitable white balance for any level of brightness ofenvironment around the apparatus.

Further, the above described HUD apparatus 7 is provided with the targetluminance input unit 600 for inputting target luminance manually by adriver or user. Instead of this manual input, an illuminance sensor 700to measure illuminance around an apparatus can be provided in a HUDapparatus 77 of variant example 1 illustrated in FIG. 9, in which theilluminance sensor 700 outputs a measurement result to the controller300, and the controller 300 sets a target luminance, with which targetluminance can be set automatically.

The automatic control can be conducted by conducting the steps shown ina flowchart of FIG. 10. In the flowchart shown in FIG. 10, a process ofsetting target luminance based on a measurement result of theilluminance sensor 700 is conducted as step S21 before step S1 in theflowchart of FIG. 7. Other steps of FIG. 10 are same as the flowchart ofFIG. 7.

Further, in the above described example embodiment and variant example1, the HUD apparatuses 7 and 77 are described as the image generationapparatus. Further, a projector 10 having a similar configuration of theHUD apparatus 7 can be provided as illustrated in FIG. 11. Further, aprojector having a similar configuration of the HUD apparatus 77 can beprovided

More specifically, as illustrated in FIG. 11, the projector 10 notincluding the lens array 60 and the semi-translucent member 70 scans asurface of the screen S as a scanned face to generate an image.

As to the projector 10, projection image luminance can be adjusted totarget luminance, and the light detector 150 can detect laser beam forany levels of target luminance.

Further, in the above described example embodiment and variant example,the optical deflection device employs a MEMS mirror that can oscillateabout two axes perpendicular to each other but not limited hereto. Forexample, as illustrated in FIG. 12, a MEMS mirror that can oscillateabout one axis can be used as a plurality of optical deflection devicesto scan a scanned face two-dimensionally. Further, for example, anoptical deflection device including a MEMS mirror that can oscillateabout one axis, an optical deflection device including a galvano mirrorthat can oscillate about one axis, and an optical deflection deviceincluding a polygon mirror that can rotate about one axis can becombined as required.

Further, in the above described example embodiment and variant example,the light adjustment member employs a configuration arranging aplurality of light passing portions having different transmittance forlaser beam with each other in one axis direction but not limited hereto.For example, as illustrated in FIG. 13, a light adjustment member thatchanges light transmittance gradually or continuously depending onpositions in one axis direction can be employed. Further, a lightadjustment member having a plurality of light passing portions havingdifferent transmittance with each other disposed about one axis can beemployed, and this light adjustment member can be rotated about the oneaxis.

Further, in the above described example embodiment and variant example,as to the light quantity adjustment device, the light adjustment memberhaving a plurality of light passing portions having differenttransmittance with each other and arranged in one axis direction can bemoved in the one axis direction but not limited hereto. For example, alight transmittance variable member that changes laser beamtransmittance depending on applied voltage (e.g., liquid crystal panelthat changes deflection or polarization angle depending on appliedvoltage) can be disposed on a light path of laser beam coming from thelight source device 15, or on a light path of laser beam emitted fromeach of laser diodes.

Further, in the above described example embodiment and variant example,as to the light quantity adjustment device 30, the light adjustmentmember 32 is disposed on a light path of laser beam (i.e., synthesizedlight) coming from the light source device 15 but not limited hereto.For example, as to a light quantity adjustment device 33 of the HUDapparatus of variant example 2 illustrated in FIG. 14, each of lightadjustment members 32 a, 32 b, and 32 c can be disposed moveably inY-axis direction on a light path between each of laser diodes andcorresponding dichroic mirrors. In this configuration, light quantityadjustment device 33 can adjust light quantity of laser beam emittedfrom the three laser diodes LD1 to LD3 independently. With thisconfiguration, correction of image quality (e.g., white balanceadjustment) can be conducted by a fine adjustment of light quantity oflaser beam emitted from at least one laser diode instead of a fineadjustment of emission light intensity of at least one laser diode, orby a combination of the fine adjustment of emission light intensity ofat least one laser diode and the fine adjustment of light quantity oflaser beam from at least one laser diode.

Further, in the above described example embodiment, the lens arrayemploys a plurality of micro lenses having a circular shape arranged inmatrix or a lattice pattern when viewed from −Z direction but notlimited hereto. For example, the lens array can employ a plurality ofmicro lenses having an N-polygonal shape (N is three or more) arrangedin a lattice pattern or a staggered pattern when viewed from −Zdirection.

Further, in the above described example embodiment and variant example,the main scanning direction is set to Y-axis direction and thesub-scanning direction is set to X-axis direction but not limitedhereto. For example, the main scanning direction can be set to X-axisdirection and the sub-scanning direction can be set to Y-axis direction.

Further, in the above described example embodiment and variant example,the configuration of the light source device 15 can be changed asrequired. For example, in the above described example embodiment andvariant example, the light source uses three laser diodes but notlimited hereto. For example, the light source can use two or less laserdiodes, and four or more laser diodes. Further, the number of dichroicmirrors can be changed depending on the number of laser diodes such aszero. For example, when one laser diode is used, a dichroic mirror isnot required. Further, instead of a dichroic mirror, a lightsynchronization prism can be used.

Further, in the above described example embodiment and variant example,a collimate lens is disposed for each of laser diodes, but the collimatelens can be omitted.

Further, the light source unit can include, for example, a lens or amirror disposed at least on a light path of laser beam between thedichroic mirror DM3 and the light adjustment member 32 and on a lightpath of laser beam between the light adjustment member 32 and theoptical deflection device 40.

Further, in the above described example embodiment, the HUD apparatus 7obtains image information from the image data output apparatus but notlimited hereto. For example, instead of the image data output apparatus,the HUD apparatus 7 can include a memory such as a storage medium orcarrier medium storing image information.

Further, in the above described example embodiment, the light detectoris disposed at a position outside the image drawing area in the mainscanning direction but not limited hereto. For example, the lightdetector can be disposed at a position outside the image drawing area inthe sub-scanning direction. Further, the light detector can be disposedat a position outside the image drawing area in the main scanningdirection and the sub- scanning direction (e.g., near a corner of thelens array 60).

Further, in the above described example embodiment, a semiconductorlaser employs a laser diode such as an edge emitting laser, but notlimited hereto. For example, a surface emitting laser such as a verticalcavity surface emitting laser (VCSEL) can be employed as a semiconductorlaser.

Further, the light detector 150 is integrally provided with the lensarray 60, but the light detector 150 can be separated from the lensarray 60.

Further, in the flowcharts of FIGS. 7 and 10, the order of steps S3 andS5 can be switched, the order of steps S7 and S8 can be switched, andthe order of steps S9, S11, and S13 can be changed as required.

Further, in the above described example embodiment, the controller 300includes a memory storing the table illustrated in FIG. 8, but thememory can be an external memory disposed outside the controller 300.Further, the number and value of parameters of the table illustrated inFIG. 8 are one example and not limited hereto. For example, the numberand value of parameters of the table can be changed as required, forexample, depending on specification of HUD apparatus, use environment ofHUD apparatus or the like.

As to the above described example embodiment, image luminance can beadjusted to target luminance and a light detector can detect laser beamfor any levels of target luminance, and an image generation apparatushaving this configuration can be provided.

The present invention can be implemented in any convenient form, forexample using dedicated hardware, or a mixture of dedicated hardware andsoftware. The computer software can be provided to the programmabledevice using any storage medium or carrier medium for storingprocessor-readable code such as a floppy disk, a compact disk read onlymemory (CD-ROM), a digital versatile disk read only memory (DVD-ROM),DVD recording only/rewritable (DVD-R/RW), electrically erasable andprogrammable read only memory (EEPROM), erasable programmable read onlymemory (EPROM), a memory card or stick such as USB memory, a memorychip, a mini disk (MD), a magneto optical disc (MO), magnetic tape, ahard disk in a server, a solid state memory device or the like, but notlimited these.

The hardware platform includes any desired kind of hardware resourcesincluding, for example, a central processing unit (CPU), a random accessmemory (RAM), and a hard disk drive (HDD). The CPU may be implemented byany desired kind of any desired number of processors. The RAM may beimplemented by any desired kind of volatile or non-volatile memory. TheHDD may be implemented by any desired kind of non-volatile memorycapable of storing a large amount of data. The hardware resources mayadditionally include an input device, an output device, or a networkdevice, depending on the type of apparatus. Alternatively, the HDD maybe provided outside of the apparatus as long as the HDD is accessible.In this example, the CPU, such as a cache memory of the CPU, and the RAMmay function as a physical memory or a primary memory of the apparatus,while the HDD may function as a secondary memory of the apparatus. Inthe above-described embodiments, at least one or more of the units ofapparatus can be implemented as hardware or as a combination ofhardware/software combination. Each of the functions of the describedembodiments may be implemented by one or more processing circuits. Aprocessing circuit includes a programmed processor, as a processorincludes circuitry. A processing circuit also includes devices such asan application specific integrated circuit (ASIC) and conventionalcircuit components arranged to perform the recited functions.

Numerous additional modifications and variations are possible in lightof the above teachings. It is therefore to be understood that, withinthe scope of the appended claims, the disclosure of the presentinvention may be practiced otherwise than as specifically describedherein. For example, elements and/or features of different examples andillustrative embodiments may be combined each other and/or substitutedfor each other within the scope of this disclosure and appended claims.

1. (canceled)
 2. An image generation apparatus comprising: a lightsource device having at least one laser that emits a laser beam; anoptical deflection device to deflect the laser beam from the lightsource device to a scanned face to generate an image thereon, and to alight detector; and processing circuitry configured to set a lightquantity of the laser beam when the laser beam is deflected to the lightdetector by the optical deflection device greater than a light quantitywhen the laser beam is deflected to the scanned face by the opticaldeflection device.
 3. The image generation apparatus of claim 2, whereinthe processing circuitry is configured to adjust an emission lightintensity of the laser to increase the light quantity of the laser beamemitted to the light detector.
 4. The image generation apparatus ofclaim 2, further comprising: a light quantity adjustment devicedisposable on a light path of the laser beam between the laser and theoptical deflection device to adjust the light quantity of the laserbeam, wherein the processing circuitry is configured to set the lightquantity of the laser beam emitted to the light detector greater thanthe light quantity of the laser beam emitted to the scanned face byusing the light quantity adjustment device.
 5. The image generationapparatus of claim 2, wherein the processing circuitry is configured tocontrol the optical deflection device based on detection timing of thelaser beam detected by the light detector.
 6. The image generationapparatus of claim 2, further comprising: a target luminance settingsensor configured to measure illuminance around the image generationapparatus, wherein the processing circuitry is configured to set thetarget luminance based on a result of the measured illuminance.
 7. Theimage generation apparatus of claim 2, wherein the light quantityadjustment device includes a member having a plurality of light passingportions, each portion having a different transmittance for the laserbeam.
 8. The image generation apparatus of claim 2, wherein the laser isa plurality of lasers, and the processing circuitry is configured toadjust emission light intensity of the laser beam emitted from theplurality of lasers for each one of the plurality of lasersindependently.
 9. The image generation apparatus of claim 4, wherein thelight quantity adjustment device includes a light transmittance variablemember that changes transmittance of the laser beam depending on anapplied voltage.
 10. The image generation apparatus of claim 2, furthercomprising: a light translucent member disposed on a light path of thelaser beam deflected by the optical deflection device, the lighttranslucent member having the scanned face.
 11. A vehicle comprising: animage generation apparatus that includes a light source device having atleast one laser that emits a laser beam, an optical deflection device todeflect the laser beam from the light source device to a scanned face togenerate an image thereon, and to a light detector, a light translucentmember disposed on a light path of the laser beam deflected by theoptical deflection device, the light translucent member having thescanned face, and processing circuitry configured to set a lightquantity of the laser beam when the laser beam is deflected to the lightdetector by the optical deflection device greater than a light quantitywhen the laser beam is deflected to the scanned face by the opticaldeflection device; and a light translucent window disposed on the lightpath of the laser beam deflected by the optical deflection device of theimage generation apparatus and passed through the light translucentmember.
 12. A method for an image generation apparatus, the imagegeneration apparatus including a light source device having at least onelaser that emits a laser beam, and an optical deflection device todeflect the laser beam from the light source device to a scanned face togenerate an image thereon, and to a light detector, the methodcomprising: setting, by processing circuitry of the image generationapparatus, a light quantity of the laser beam when the laser beam isdeflected to the light detector by the optical deflection device greaterthan a light quantity when the laser beam is deflected to the scannedface by the optical deflection device.